Low cost autotransformer



1965 J. ANDERSON LOW COST AUTOTRANSFORMER Filed Dec. 19, 1962 A 7 W F FIG.2

N 0 S MR E D N VA N L N H 0 d ATTORNEY tory .equipment, motor speed controls and the like.

United States Patent 3,202,949 LOW CGST AUTQTRANSFORMEP.

John L. Anderson, Poughkeepsie, N.Y., assignor to International Business Machines Corporation, New York, N.Y., a corporation of New York Filed Dec. 19, 1962, Ser. No. 245,759

9 Claims. (Cl. 336-149) This invention relates to transformers and more particularly to a variable transformer of the single winding orautotransformer type.

Autotransformers are well known in the art and generally include a coil energized with a predetermined A.C. voltage. A sliding tap picks off a desired voltage anywhere from ,zero up to :the energizing voltage. Transformers of this type are used in power supplies, labora- In many cases the dimensions of such transformers are greatly restricted in their application by the space available.

It is the object of this invention to provide a variable transformer that is easily assembled from simple inexpensive parts.

A further object is to provide a variable transformer that is small but rugged and has a minimum number of parts.

Another object is to provide an autotransformer that is operable from either side of a panel. A midsection of the autotransformer is mounted on the panel and manipulative knobs extend from both faces of the panel.

The foregoing and other objects, features and advantages of the invention Will be apparent from the following more particular description of the preferred embodiment of the invention, as illustrated in the accompanying drawings.

.In the drawings:

.FIG. 1 is an exploded view-showing the members of the device of the invention.

FIG. 2 is a cross section taken longitudinally the center of the device.

As can .be seen in FIG. 1 the device comprises three major parts; two knobs and a central body portion or encasement. The knob 10 is dishshaped with a pointer 11 and molded of any Well known thermosetting polyester resin or other insulation material. .A metal insert 12 having a short shaft and a keying hexagonal head is molded into the center of the dished cavity 14. A groove 15 (FIG. 2) provided at the bottom of the cavity is used to lock the members together as Will be explained below.

The body portion or casing'16 is molded as shown of any suitable heat conductive plastic such as aluminum oxide epoxy. Embedded in the body is the usual transformer 17 comprising a toroidal magnetic core 18 and a toroidal winding 20. The input and output terminals are molded in the body'16. Terminals 21 and 22 are the input terminals for the toroidal winding 20. Terminal 23 is connected to a tap on a section of the Winding adjacent one end thereof and the input voltage can be connected to terminal 23 rather than terminal 21 thereby providing a maximum output voltage somewhat higher than the input voltage. The output voltage is taken from the terminal 23 and terminal 24 that is connected to a slip ring to be described below. The body 16 is provided with hollow collars or flanges 25 and 26. The collar 25 has a lip 27 adapted to engage the groove 15 in the knob 10. The collar 26 has a metallic slip ring 28 preferably of copper molded therein which forms a lip that engages a groove 31 in the lower knob. The slip ring 28 is connected to a terminal 24 by a conductor 29 molded in the collar 26.

The lower knob 30 is molded as shown of a plastic similar to that used for knob 10. It is dish shaped and has through 32%,942 Patented Aug. 24, 1965 the groove 31 adapted to receive lip 28 when the device is assembled. Molded in the center of the dished portion is a spool shaped shaft 32 having a hexagonal orifice 33 formed in the top which is adapted to mate with the hexagonal head 12 when the device is assembled. Molded in the bottom of the dished portion is a ring 34 preferably of copper having an upstanding arm 35 to which is fastened by any well known means, such as Welding, a narrow resilient contact brush 36 of any suitable material such as Phosphor bronze. This brush is adapted to wipe over and make contact with the inner surface of the winding 20 that has been bared by being cleaned of all insulation.

In assembling the parts, the knob 10 is forced or snapped over the collar 25 until the lip 27 engages the groove 15 thus forming a bearing for the knob. The spool shaped shaft 32 is now inserted into the collar 26 of body 16 until the slip ring 28 engages or snaps into the groove 31 and the keying hexagonal end of insert 12 keys into and engages the hexagonal orifice in the shaft 32. An electrical wiping contact is established between rings 28 and 34. Rotation of either knob will cause the brush 36 to wipe the wires of toroidal winding 20. This will complete a circuit from terminal 23 through a portion or all of toroidal winding 20, brush 36, lead 35, ring 34, slip ring 28, conductor 29 to terminal 24. By this circuit more or fewer coils of winding 20 are connected in the circuit thus varying the output voltage. Although rings 28 and 34 are shown to be of substantial thickness, they could be merely curved rings of sheet metal mating at the rounded edge of slip ring 28.

It is obvious that the two knobs 10 and 3t) permit the operation of the device from both sides. Consequently it can be mounted on a panel and operated from the front or rear. Ears 37 are provided for mounting screws. Numerals 38 molded on the base 16 give an indication of the selected output voltage.

While the invention has been particularly shown and described with reference to a preferredembodiment thereof, it will be understood by thse skilled in the art that the foregoing and other changes in form and details may be made therein without departing from the spirit and scope of the invention.

What is claimed is:

1. A variable transformer comprising:

a toroidal magnetic core having an open center and a vcoil wound thereon and insulated therefrom,

a casing molded about said core exclusive of said center,

a pair of knobs having shafts thereon extending into said coil in interlocking relation,

lips on said casingengaging and locking said knobs in rotatable relation therewith,

contact means comprising one of said lips engaging a second contact on one of said knobs, and

a resilient contact .on the shaft of said last mentioned knob making contact with the center of said coil, said resilient contact being connected to said second contact, whereby rotation of either of said knobs will vary the potential output of the transformer.

2. A variable transformer comprising:

a magnetic toroidal core having an open center and a coil wound thereon and insulated therefrom,

a casing of heat conductive material molded about said core exclusive of said center, said casing having extending collars,

terminals molded in said casing connected to said winding for energizing said coil,

a pair of knobs having shafts thereon extending into said coil in interlocking relation,

lips on said collars engaging and locking said knobs in rotatable relation therewith,

a slip ring comprising one of said lips engaginga contact ring on one of said knobs, and

a brush on the shaft of said last mentioned knob making wiping contact with the center of said coil, said brush being connected to said ring, whereby rotation of either of said knobs will vary the potential output of the transformer.

3. A variable transformer comprising:

a magnetic toroidal core having an open center and a coil wound thereon and insulated therefrom,

a plastic casing molded about said core exclusive of said center, said casing having a pair of hollow collars extending therefrom,

said coil having that portion of Winding in the center thereof bared of insulation,

a pair of knobs having shafts thereon extending into said coil in interlocking relation,

lips on said collars engaging and locking said knobs in rotatable relation therewith,

a contact comprising one of said lips engaging a second contact on one of said knobs, and

I a brush on the shaft of said last mentioned knob making wiping contact with the bared portion of said coil, said brush being connected to said contact, whereby rotation of either of said knobs will vary the potential output of the transformer.

4. A variable transformer comprising:

a magnetic core having an open center and a coil wound thereon and insulated therefrom,

a casing of heat conductive plastic molded about said core exclusive of said center,

terminals molded in said casing connected to said winding for energizing said coil,

said coil having that portion of the winding in the center thereof bared of insulation,-

a pair of knobs having shafts thereon extendin into said coil in interlocking relation,

lips on said casing engaging and locking said knobs in rotatable relation therewith,

a slip ring comprising one of said lips engaging a contact ring on one of said knobs, and

a brush on the shaft of said last mentioned knob making wiping contact with the center of said coil, said brush being connected to said ring, whereby rotation of either of said knobs will vary the potential output of the transformer.

5. A variable transformer comprising:

a toroidal core with an insulated winding, the portion of said winding in the center of said core being bared,

a casing of a heat conductive material molded about said core and winding, said casing having end flanges one of which is conductive as a slip ring,

a first knob for engagementwith said slip ring and carrying an interior shaft portion,

a contactor on said shaft portion for adjustable contact with said bared winding, and

a second knob having a keying shaft extension adapted to engage the other of said end flanges and key into said shaft portion to permit movement of said contactor by either knob.

6. A variable transformer comprising:

a toroidal core with an insulated winding, the portion of said winding in the center of said core being bared, r

a plastic casing molded about said core and Winding,

said casing having end flanges each acting as a beara a first plastic knob having a groove therein for engagement with one of said flanges and carrying an interior shaft portion,

a contactor on said shaft portion of said first knob for adjustable contact with said bared Winding, and

a second plastic knob having a key extension and adapt,-

'ed to engage the other of said flanges and key onto said shaft portion to permit movement of said contactor by either knob.

7. A voltage control device comprising: a

a toroidal core with an insulated winding, the portion of said Winding in the center of said core being bared,

a plastic casing of a heat conductive material molded about said core and winding and having end flanges one of whichis conductive as a slip ring,

a first plastic knob for engagement with said slip ring and carrying an interior shaft portion,

a contactor on said shaft for adjustable contact said bared Winding, and

a second plastic knob having a key end and adapted to engage the other of said end flanges and key onto with said shaft portion to permit movement of said contactor by either knob. 8. A device of the kind set forth in claim 7 wherein said Winding comprises a coil of a' single wire layer in one continuous length of Wire with a plurality of intermediate and end terminals.

9. An autotransformer comprising:

a toroidal metallic core with a'winding of a plurality of tapped sections with Wire exposed around an inner ring,

a plastic outer encasement for said core, said encasement being hollow and formed with end flanges one 'of which is conductive as a slip ring,

a firstplastic knob for fitting onto said slip ring and carrying an interior shaft and contactor for adjustable contact With said exposed wire in said Winding sections, V i

and a second plastic knob for fitting onto the opposite flanged end of said encasement and engaging the first knob to hold said interior shaft in place and keyed to both knobs.

References Cited by the Applicant UNITED STATES PATENTS 2,009,013 7/35 Karplus et al. 2,985,857 5/61 Ellin et al. 3,087,132 4/63 Snowdon et al.

- JOHN F. BURNS, Primary Examiner. 

1. A VARIABLE TRANSFORMER COMPRISING: A TOROIDAL MAGNETIC CORE HAVING AN OPEN CENTER AND A COIL WOUND THEREON AND INSULATED THEREFROM, A CASING MOLDED ABOUT SAID CORE EXCLUSIVE OF SAID CENTER, A PAIR OF KNOBS HAVING SHAFTS THEREON EXTENDING INTO SAID COIL IN INTERLOCKING RELATION, LIPS ON SAID CASING ENGAGING AND LOCKING SAID KNOBS IN ROTATABLE RELATION THEREWITH, CONTACT MEANS COMPRISING ONE OF SAID LIPS ENGAGING A SECOND CONTACT ON ONE OF SAID KNOBS, AND A RESILIENT CONTACT ON THE SHAFT OF SAID LAST MENTIONED KNOB MAKING CONTACT WITH THE CENTER OF SAID COIL, SAID RESILIENT CONTACT BEING CONNECTED TO SAID SECOND CONTACT, WHEREBY ROTATION OF EITHER OF SAID KNOBS WILL VARY THE POTENTIAL OUTPUT OF THE TRANSFORMER. 